The objective of the research is to chemically identify the androgens and estrogens present in insects and to define their physiologic role(s). Gas chromatography-mass spectrometry will be used to determine the chemical identity of the steroids. Various tissues from flesh flies (Sarcophaga bullata) will be analyzed for the presence of androgen and estrogen receptors using radioligand binding experiments. Steroidal precursors of the androgens and estrogens will be identified by tracing the fate of radiolabeled compounds such as cholesterol. Properties of the enzyme aromatase will be examined and compared to the mammalian enzyme. The source of androgens and estrogens will be determined by measuring steroid levels in select tissues and by monitoring in vitro the release of androgens and estrogens into culture medium. Endogenous levels of androgens and estrogens in flesh flies will be monitored by RIA as a function of developmental stage, age, sex, mating status, diapause, and circadian time. The efficacy of exogenous androgens and estrogens in altering sex ratios, mating behavior, egg maturation, and survival will be tested. The role of the neuroendocrine system and gonads in regulating hemolymph androgen and estrogen levels will be evaluated by surgical extirpation of select organs and application of exogenous ecdysteroids and juvenile hormone analogs. The discovery of andronges and estrogens in insects introduces a new class of compounds that may play important roles in insect development and reproduction and may thus augment strategies for the control of pest species.